Combined desensitizer and developer and process of desensitizing and developing



Patented May 21, 1929,

UNITED STATES PATENT OFFICE.

HERBERT MEYER, 01' BEBLIN-TBEPTOW, GERMANY, ASSIGNOB, 3T KESNE ASSIGN- I IENTS, TO AGFA ANSOO CORPORATION, 01' BINGHAITON, NEW YORK, A CORPORA- TION or NEW Yoax.

COMBINED DEBENBITIZEB AND DEVELOPER AND PROCESS 01' DEVELOPING.

DESENSITIZING AND No Drawing. Application filed September -8, 1827, Serial 1T0. 818,385, and in Germany Ioyember 13, 1928.

The present invention'relates to new photographic developers, more particularly to photographic developers comprising the cyanide of a heavy metal. It relates further- 5 more to the process of developing photographic surfaces with the aid of-the new devclopers.

I have found that the cyanides of the heavy metals act as good 'desensitizers when added to a photographic developing agent i. e. their presence in the developing agent permits photographic surfaces to be developed either wholly or in greater part in full light without diminishing the latent image. As compared with the known desensitizing dyestuffs the cyanides of the heavy metals have the advantage that they do not color the developer, or the developed sensitive materials. In addition they remain active for a much longer time in concentrated developing solutions for example, in concentrated hydroquinonedevelopers;

I have furthermore found that the cyanides of the heavy metals have a pronounced antifog action so that'with their aid not only the known time developers are improved, but any developin agent can be made suitable for time deve opment.

I prefer to use mercur cyanide which is especially eflicient, but t e eyanides of the other heavy metals may be used also, as for instance cobalt or cadmium-cyanide, al-

though they are not quite as efliclent as mercury cyanide.

Generally it will be sullicient to add about 0.03 arts by weight of mercury cyanide to the eveloping agent. It makes no difference as to the action of the cyanide whether it is added to the developing agent itself or to the solution formed therefrom.

Ezample I.To a monomethyl-para-ami- I nophenol-sulphate-hyd uinone developer, mercuric cyanide is add in the proportion of 0.3 gram to 1000 cc. of the develo exposed material to be developed is eveloped graphic developer comprising r. The

in a room. having usual dark room illumination for A to 2 minutes, whereupon a further development is carried out in a bright yellow light, as is usual in operating with the known dyestufi desensitizers.

Eaiample 2.A monomethyl-para-aminophenolsulphate-hydroquinone developer, in which the exposed material to be developed would acquire a considerable fog as the cf fect of 10 minutes development, receives an addition of 0.3 gram of mercuric cyanide per 1000 cc. of developer. The same material may now be developed under normal dark room illumination in this develo r contain ing cyanide for 20-50 minutes without showing appreciable fog after fixing.

I claim: 7

1. As new compositions of matter photographic developers comprising theeyanide of a heavy metal.

2. As new compositions of matter photogra hic developers comprising mercury cyam e.

3. As a new composition of matter aphotomercury cyanide, monomethylpara-amlnophenol sulphate and hydroquinone.

. 4. A process of desensitizing and developing exposed silver halide sensitized elements, which com rises subjecting them to the action of a p otographic developer containing a cyanide of a heavy metal.

.5. A process of desensitizlng ing exposed silver halide sensitized elements, which comprises subjecting them to the action of a photographiedevelo'per containing mercury cyanide.

6. A process of desensitizing and developing exposed silver halide which com rises subjecting them to the action of a photographic developer containing mercury cyanide, monomethyl-para-aminophenol-sulphate and hfvI uinone.

Intestimon whereo m si ature.

Dm HERBERT ZIETER.

and developsensitized elements, 

